1. Field of the Invention
The present invention relates to hearing aids. The invention, more specifically relates to an earplug for a hearing aid and a hearing aid with an earplug, in particular a soft earplug for a BTE-type hearing aid.
2. The Prior Art
BTE-type hearing aids generally have a hearing aid housing comprising a hard shell in which all of the electronics, including input and output transducers, of the hearing aid are typically located. The hard shell is worn Behind The Ear, hence the abbreviation BTE. If the output transducer is located in the hearing aid housing, the output sound from the hearing aid is conducted via a sound tube to an earplug placed in an ear of the person wearing the hearing aid. Both the sound tube and the earplug constitute replaceable parts, which can be, and normally are, replaced with regular intervals. The earplug, which is in direct contact with the ear, is typically replaced more often than the sound tube, because it is more prone to be soiled, e.g. by cerumen.
Since the earplug is frequently replaced, it is not desirable to provide it as an individually fitted piece i.e. adapted to the specific shape of the ear canal of the wearer. Rather, it should be provided as a soft plug, which is comfortable to wear, by any person, irrespective of the specific shape of the ear canal. In practice however, even soft earplugs will not fit any person, but have to be provided in a few different lengths and diameters, e.g. two or three, in order to fit both children and adults.
Regarding comfort, it is also desirable to provide an earplug, which does not completely block the ear canal. Blocking the ear canal completely leads to the uncomfortable occlusion effect, where distorted sounds transmitted through bones and other tissue become more predominant.
One type of soft earplug is marketed by the company GN Resound, Taastrup, Denmark. This earplug could roughly be described as having a mushroom shape with a fourth order rotational symmetry along a center axis. The earplug comprises a central part comprising a longitudinal bore and one sound output opening in communication with said longitudinal bore, a collar surrounding said central part and adapted to engage the wall of an ear canal, and four sound passages communicating with the environment outside of the ear canal, the sound passages being provided between said collar and said central part. The sound output opening is located axially at the tip of the front end inserted into the ear canal, i.e. concentrically with the axis of the rotational symmetry. The earplug is made from silicone rubber, which is injection mounded and subsequently vulcanized.
EU design no. 000007893-0001, registered on 1 Apr. 2003, shows a hearing aid with an earpiece.
Designing an earplug with an axial opening at the tip, however, incurs a risk that on inserting it in the ear, cerumen may enter the sound output opening. If this happens, the sound produced by the hearing aid cannot leave the plug, thus adversely affecting the proper function of the hearing aid.
Providing a selection of standardized earplugs may not be sufficient to ensure, that each and every wearer can get a satisfactory fit. That is to say, the ear canal may for the specific user have such a shape that when the earplug is inserted into the ear canal, it always or mostly ends up in a position, in which the sound output opening is blocked by the wall of the ear canal.
The company Bruckhoff Apparatebau, Hannover, Del., supplies an attachment for the sound tube of hearing aids. This device is marketed under the name Cerumen Defenser (CD). This attachment cannot be considered to be an earplug, as it does not engage the ear canal. Instead it is held freely in the ear canal supported only by the sound tube. This device is generally cylindrical with a central bore. From the central bore, sound output openings extend axially away from the sound tube as well as transversely in the radial direction. This known device has been shown on the internet, <URL: http://www.bruckhoff-apparatebau.com/zub-allg.htm> 31 Jan. 2005.
Though not specifically for a hearing aid, a further earplug is known from U.S. Pat. No. 3,934,100. This earplug has a single sound output opening at the very tip of the earplug in the insertion direction.